lift the declarations without mutating the node[fix #402] (#403)

* lift the declarations without mutating the node[fix #402] * add test case for capturing regression
babel · Feb 2, 2017 · 1211936 · 1211936
1 parent d7324f7
commit 1211936
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Showing 2 changed files with 20 additions and 3 deletions.
diff --git a/packages/babel-plugin-transform-merge-sibling-variables/src/index.js b/packages/babel-plugin-transform-merge-sibling-variables/src/index.js
@@ -24,9 +24,7 @@ module.exports = function({ types: t }) {
         return;
       }
 
-      init.node.declarations = init.node.declarations.concat(
-        firstNode.id
-      );
+      init.pushContainer("declarations", t.variableDeclarator(firstNode.id));
 
       body[0].replaceWith(t.assignmentExpression(
         "=",

diff --git a/packages/babel-preset-babili/__tests__/preset-tests.js b/packages/babel-preset-babili/__tests__/preset-tests.js
@@ -75,4 +75,23 @@ describe("preset", () => {
     `);
     expect(transform(source)).toBe(expected);
   });
+
+  it("should fix issue#402 - lifting var decl & DCE", () => {
+    const source = unpad(`
+      function a() {
+        if (0) {
+          for (var i;;) {
+            var something = 5;
+          }
+        }
+      }
+      a();
+    `);
+    const expected = unpad(`
+      function a() {}
+      a();
+    `);
+    expect(transform(source)).toBe(expected);
+  });
+
 });